Barry, I found this:

"Biarritz is one of the few cities of France where you will find casinos. You have 2 casinos there: The first one is the casino municipal which is pretty much casual, it has been redone few years ago, and the inside has made redesigned by Willmote a famous French architect who designed the Champs Elysees. The second one is the casino Bellevue which more dressed up. Just depending what you are looking for. FYI, the casual meaning is different in France than in many other countries. Do not try to get in in shorts and slaps!"